Method and apparatus for treating wells



Oct. 5, 1965 c. T. SAUERS ETAL 3,209,833

METHOD AND APPARATUS FOR TREATING WELLS 5 Sheets-Sheet 1 Original Filed Sept. 20, 1957 INVENTORS'. 019491615 7: 55405915 650/9675 L. M414 Oct. 5, 1965 C. T- SAUERS ETAL METHOD AND APPARATUS FOR TREATING WELLS Original Filed Sept. 20, 195'? 3 Sheets-Sheet 2 N1|UM 1955 c. T. SAUERS ETAL METHOD AND APPARATUS FOR TREATING WELLS Original Filed Sept. 20, 1957 5 Sheets-Sheet 3 I E Fi ldlll!51111173559515:

United States Patent 3,209,833 METHOD AND APPARATUS FOR TREATING WELLS Charles T. Sauers, Ontario, and George L. Malan, Co-

vina, Calif., assignors to Dyna-Frac, Inc., South El Monte, Calif., a corporation of California 7 Continuation of application Ser. No. 685,145, Sept. 20, 1957. This application June 19, 1961, Ser. No. 120,871

SClaims. (Cl. 166-177) This is a continuation of co-pending US. application Serial No. 685,145, filed September 20, 1957, now abandoned.

This invention relates to a process for breaking up materials that tend to seal off the flow in wells, and also provides apparatus for carrying out the process. The process is especially useful in treating oil wells to break up accumulations of matter in the immediate vicinity of the well bore which tend to seal off the flow of oil and gas, and is also useful in treating water wells in cases where similar conditions exist.

Declining oil and gas production in older wells and low production in newly completed wells, where the potential production is high, are problems for which the oil industry has long sought practical solutions. There are a variety of causes to which low production in potentially high producing regions may be attributed. The cause with which we are here concerned is the formation or accumulation of relatively impervious deposits immediately surrounding the bare well bore or perforated liner in the producing region. Such accumulations may be formed by mechanical or chemical action, or both, over a period of time, and may comprise scale, mud, sand, shale, wax, clay, resin, common sludge, and other residuals that have become fixed on the inside surface of the casing, in the casing perforations, between the casing and the oil bearing formation, and within the pores and fissures in the oil bearing formation adjacent the well. In the completion of a new well, a seal can be produced where the drilling mud employed is, because of the high mechanical forces involved, forced into the pores and fissures in the oil bearing formations immediately surrounding the well bore.

To gain more than mere temporary relief from this type of condition, it is necessary to break up and remove substantial amounts of the sealants. This is presently accomplished with explosives and chemical solvents. However, use of explosives sometimes does more harm than good, and both the explosive technique and the chemical solvent technique can be expensive, and any resulting increase in production may be short-lived. In many instances, the possibility of increasing production does not justify the expense and risks involved. Hence, there remains a great need for more practical and effective methods for increasing production in wells where such seals exist.

The method of the present invention involves the use of a particular kind of mechanical vibrations in accordance with a prescribed technique, and is both practical and effective in breaking up such seals. In the past, employment of vibrations in wells has not succeeded in breaking up the sealants of concern here, probably because the sealants are usually somewhat plastic and cohesive, and are little affected by ordinary sonic disturbances. Hence, the conventional employment of vibrations in wells has been carried out mainly on the theory that the surrounding strata affords, while it is subjected to sonic disturbance, a lesser resistance to the flow of oil therethrough. However, in experiments conducted in liquid-filled oil well casings, we have found that by employing a compact source of mechanical vibrations of the type which produces a rotating force vector in a lateral plane so as to both vibrate and torque the surrounding medium, and by sufliciently increasing the power that drives the source, a point is finally reached where such sealants are broken up, and substantial amounts thereof are carried into the liquid medium through perforations in the oil well casing.

We have found that by employing a compact vibration source submerged in a liquid medium, it is practical to achieve a suflicient vibratory energy concentration in the immediate vicinity of the source to produce this effect. In our experiments we have employed a compact fluiddriven vibrating head similar to that disclosed in U.S. Patent No. 2,743,090, dated April 24, 1956. This head has a gyrating element contained in a cylindrical race, and produces a rotating force vector in a lateral plane, i.e., in a plane transverse to the axis of the cylinder and to the longitudinal axis of the well. We estimate that such a source must be driven on a continuous basis and at a power level suflicient to cause it to dissipate vibratory energy into its surroundings at a rate of at least 15,000 foot pounds per minute, in order to begin to attain the desired effect. Of course, it is desirable, and sometimes necessary, to operate the source at higher power levels.

By movably suspending the compact source within the well, and moving the source along the length of the well in the producing region, the entire producing region immediately adjacent the well, after a time, can be subjected to a vibration energy density which would be impractical to achieve if it were attempted to be supplied over a substantial length of the well all at once. Also, by employing a fluid driven type of vibrating source, and supplying driving fluid to the source from a reservoir and power plant located externally of the well, the driving fluid tends to dissipate heat and the driving power is continuously available and relatively unlimited, so that the vibrating source may be driven continuously at a high power rate over substantial periods of time.

In order to properly suspend and eflectively operate a fluid driven vibrating head within the confines of a well bore or the like, we have devised an elongated hanger assembly. This hanger assembly includes a central conduit which defines a central passageway for carrying the supplied driving fluid. Means are disposed inside the central conduit for filtering the driving fluid before it reaches the vibrating head. The lower end of the central conduit is coupled to the intake port of the vibrating head by a hose. The hose is made of flexible material, so as to reduce the loss of vibratory energy from the vibrating head to the central conduit. The central conduit is surrounded by an outer conduit, with an annular passageway between the two for carrying the exhausted driving fluid. Mechanical means, including means which affords a high impedance to transmission of vibratory energy from the vibrating head to the outer conduit, surrounds the hose and couples the lower end of the outer conduit to the vibrating head, so that the annular exhaust passageway communicates with the exhaust port of the vibrating head. Means are included for supporting the central conduit on the outer conduit.

Employing a conventional derrick and elevating mechanism, the hanger assembly and attached vibrating head may be lowered into the well by connecting successive sections of pipe together in conventional fashion' The first section is connected to the upper end of the outer conduit of the hanger assembly. A second string of pipe sections of smaller diameter may be connected to the upper end of the central conduit of the hanger assembly for conveying the driving fluid thereto, with the exhausted driving fluid being carried by an annular space between the two strings of pipe. The vibrating head is movably suspended by the elevating mechanism, the weight being carried by the larger diameter pipe and the outer conduit of the hanger assembly.

The method and apparatus of the invention will be understood from the following description, taken in conjunction with the drawings; in which,

FIG. 1 is a schematic drawing, partially in section, illustrating the employment of a compact vibrating head in an oil well according to the method of the invention;

FIG. 2 is a fragmentary schematic drawing, partly in section, illustrating in greater detail the vibrating head of FIG. 1 within the well;

FIG. 3a is a fragmentary view, partly in section, of the upper portion of the hanger assembly of the invention;

FIG. 3b is a fragmentary view, partly in section, of the central portion of the hanger assembly; and,

FIG. 30 is a fragmentary view, partly in section, of the lower portion of the hanger assembly, with the attached vibration head.

Referring now to FIGS. 1 and 2, a compact vibrating head is movably suspended within an oil well 12 by means of a string of supporting steel pipe sections 14, coupled to a conventional elevating mechanism 16, rigged to a derrick 18 and operated by a conventional power plant 19. The vibrating head is disposed in a liquid 20 within the well, which liquid is usually oil containing some water and other impurities. If a well does not already contain suflicient liquid to cover the zone of the well to be treated, it is necessary to fill the well with some liquid such as oil. Of course, if a water well is being treated, water is preferred.

As illustrated, the well is equipped with a steel liner 22, having perforations 24 in the producing region, so that oil and gas can move into the casing from oil bearing formations 26, 28; however, the process of the invention is also applicable to wells having bare walls.

The vibrating head is a gas driven source of direct lateral vibrations, such as that disclosed in US. Patent No. 2,743,090. The driving gas is supplied from a portable air compressor 30, deriving air from the atmosphere. The air compressor is equipped with a hose 32, which is coupled to the upper end of a string of small diameter pipe sections 34 (see FIGS. 2 and 3a) located inside the string of outer supporting pipe sections 14. The hose is made of flexible material and wound on a reel 36 to allow for the raising and lowering of the elevator assembly 16, necessary to move the vibrating head 10 along the well bore.

A portion 38 of what appears to be part of the string of supporting pipe sections 114, located between a connecting collar 4d and the vibrating head, is in reality a hanger assembly of special construction for properly suspending and operating the vibrating head within the confines of the well.

As best illustrated in FIGS. 3a, 3b, and 3c, the hanger assembly comprises a central conduit 42 defining a central passageway 44 for carrying the supplied driving gas, and an outer conduit 46 surrounding the central conduit and defining the outside of an annular passageway 48 for carrying the exhausted driving gas. The gas flow is in dicated by the arrows.

The lower end of the central conduit, located at 50, is connected by means of a flexible hose 52 to a fixture 54 that defines the intake port of the vibrating head.

The lower end 56 of the outer conduit is coupled by mechanical means 58 to the vibrating head, so that the annular passageway connects with the exhaust port, or ports, 60 of the vibrating head.

The central conduit is connected to the outer conduit by a perforated pipe 62, which is intermediate in diameter between the outer conduit and the hose 52. The connecting pipe 62 is attached at its upper end to the central conduit by means of a welded insert 63. It extends coaxially with the hose 52 for a distance, and is connected at its lower end to the outer conduit, the latter connection being made through an intermediate member 65 to which the connecting pipe is welded with the intermediate member 65 being in turn welded to the outer conduit. Hence, the outer conduit carries the weight; and, because of the perforations in the connecting pipe, there is no interference in the exhaust gas stream, as depicted by the arrows.

The central conduit includes an enlarged portion 64 having an upstream opening 66, and a downstream opening 68. A first perforated pipe 70 is coupled to the upstream opening for discharging driving gas into the enlarged portion and at the same time filtering out any large particles which may be present in the gas stream. A second perforated pipe 72 is coupled to the downstream opening. A screen 74- is disposed around the second perforated pipe, so that fine particles in the driving gas flowing into the second perforated pipe from the enlarged portion are filtered out. Because the process involves vibration, and because there is a long string of small pipe 34 through which the gas must travel before it arrives at the vibrating head, there is a substantial likelihood that particles may flake oif from the interior of the small pipe, particularly at the connections. Such particles would foul the vibrating head. This is prevented by the location of the filters at positions near the vibrating heads inside the central conduit of the hanger assembly.

The mechanical means 58, which couples the lower end of the outer conduit to the vibrating head, includes a hollow cylindrical member 76 having a rounded collar portion 78 protruding from its exterior surface. A rubber gasket 80 overlies and surrounds the rounded collar portion, and a hollow cylindrical assembly 82 overlies the rubber gasket and is separated by the gasket from the cylindrical member. The cylindrical assembly includes a lower portion 84 and an upper portion 86. The upper portion screws into the lower portion so that the assembly tightens down on the gasket, yet remains separated and out of contact with the cylindrical member. Hence, the only mechanical connection between the vibrating head and the hanger assembly is through the rubber gasket and the hose. Both of these are composed of a flexible material such as rubber, and so tend to reduce the loss of energy from the vibrating head to the hanger assembly and above. Otherwise, it would be difiicult to achieve a proper concentration of vibratory energy at the head.

The cylindrical member has two additional collars, 88, 90, located respectively above and below the rounded collar portion. These additional collars are large nuts screwed onto opposite ends of the cylindrical member. They are spaced at short distance from the cylindrical assembly 82 to limit the extent of any movement thereof relative to the cylindrical member, in case the vibrating head strikes against any object when it is being lowered into a well, or in case the vibrating head becomes stuck in the well and has to be pulled out.

The cylindrical member is connected at its upper end to the lower end of the outer conduit by a threaded collar 92.

A loose-fitting rubber doughnut 94 is disposed around the outer conduit and centers the hanger assembly and vibrating head within the well so that the vibrating head is maintained out of contact with the walls of the well. The diameter of the doughnut is somewhat greater than that of the vibrating head, and it is loosely held in place by two snap rings 96, 98, so that it does not travel up and down the outer conduit. Maintaining the vibrating head out of contact with the walls of the well is of importance mainly when high power rates are employed in older wells, because it has been observed that the vibratory energy level involved can cause the rupture and collapse of steel oil well casings.

The mechanical details of the connections employed between the paths in the hanger assembly are not described in detail, because they are conventional. Any type of secure connections will sufiice.

Preferably, the hanger assembly is made of sections of steel pipe. At the upper end of the hanger assembly, there is the collar 40 screwed onto the outer conduit; and a collar 100 defines the upper end of the central conduit.

To locate the vibrating head in the producing region of a well, the elevator mechanism 16 is employed in the usual manner to add section after section of steel pipe 14 to the outer conduit of the hanger assembly until the vibrating head reaches the producing region. The pipe is then anchored, leaving the elevator mechanism free. Once this has been accomplished, the elevator mechanism is employed to make up and lower the smaller diameter sections of pipe 34 inside the larger pipe until the leading end of the small pipe abuts the threads on the collar 100. Then the small pipe is screwed into the collar. At this point the hose 32 from the air compressor is coupled to the upper end of the small pipe, and the elevator is reattached to the large pipe for raising and lowering the entire pipe string including the vibrating head.

To facilitate the making up of the pipe string in accordance with the above description, the small pipe has welded on its lower end a plurality of fins, such as that shown at 102, which center the small pipe within the supporting or large pipe, and serve as a guide for causing the lower end of the small pipe to meet the open end of the collar 100. Similar fins are employed at spaced locations along the small pipe to keep it centered.

With the equipment in place, it operates as follows:

Driving fluid, preferably air, is forced under high pressure through the flexible hose 32 to the small pipe 34, which carries it to the upper end of the central conduit of the hanger assembly and thence to the intake port of the vibrating head. The air exhausted from the vibrating head is carried up the annular passageway 48, up the annular gap between the large and small pipe, and out the open end of the large pipe. The air pressure is increased until the vibrating head begins to dissipate energy into its fluid surrounding at a rate high enough to cause the sealing materials to break. The vibrating head is then moved slowly along the bore in the producing region of the well. This breaks the sealants and carries them into the well bore. The sealants tend to accumulate at the bottom of the well, and may be bailed out after removal of the vibrating head.

Depending upon the viscosity of the liquid in the well, particularly after emulsification by the tremendous concentration of vibratory energy, and perhaps depending upon the pressure at the point the vibrating head is being operated, the liquid may tend to cavitate. As used here, the term cavitate means the tendency of the liquid, when sufliciently energized over a period of time, to pull away from contact with the vibrating head. In other words, the liquid is bounced away from the head, so that voids are formed. This impedes the transmission of vibratory energy to the surrounding sealant. In order to preclude such an occurrence the vibrating head may be moved along the bore continuously at a slow rate. We have found that a rate of three feet per minute is sufiiciently high to prevent cavitation in an oil medium with a hydrostatic head of approximately five feet.

When air is employed as a driving fluid, it should be exhausted outside of the well because of its oxygen content. Even when an inert driving gas is used, it should be exhausted at a point above the driving head, so that it does not interfere with the transmission of vibratory energy through the liquid medium to the surrounding structure, in a fashion similar to the interference caused by cavitation in the liquid medium.

Our experiments indicate that it is desirable, if not necessary, to produce sustained lateral vibrations having a considerable amplitude, so that a strong surging effect is produced in the liquid medium causing it to wash as well as transmit vibration energy to the surrounding structure. In our work to date, we have not been able to produce a satisfactory effect at a vibration frequency of less than 3,000 cycles per minute, which seems to indicate that the vibration source must be vibrated at a double amplitude of at least & inch, or thereabouts, to produce the desired effect. Best results have been obtained at frequencies of approximately 10,000 cycles per minute. In these cases, the head was vibrating at a double amplitude of approximately A inch. This seems to indicate that a large amplitude type of vibration is required.

Conditions in one well will not be the same as they are in other wells, and well bore sizes vary. In consequence, the vibratory energy required will vary to some extent. We have been most successful when operating the vibrating head so that it dissipates vibratory energy into the liquid surroundings at an estimated total rate of at least 24,000 foot pounds per minute. The vibrating head which we employed occupied about fourteen inches of vertical section in the well. So 24,000 foot pounds per minute would correspond to an average vibratory energy density of approximately 1700 foot pounds per minute per inch of vertical section of the well. Based upon our experiments, a vibratory energy density corresponding to at least 15,000 foot pounds per minute dissipated within a thirty inch vertical section of the well must be provided in order to begin to achieve a successful effect; or 500 foot pounds per minute per inch.

Chemical solvents and the like may be employed in the liquid medium within a well, to augment the results of the process of the invention.

We claim:

1. In apparatus for producing mechanical vibrations including a fluid driven vibrating head having intake and exhaust ports for the driving fluid, the improvement which comprises an elongated hanger assembly for suspending and operating said vibrating head within the confines of a well bore at locations above the bottom of the well, said hanger assembly comprising a central conduit for carrying the supplied driving fluid, means disposed inside the central conduit for filtering the driving fluid before it reaches the vibrating head, a hose of flexible material coupling the lower end of the central conduit to the intake port of the vibrating head, an outer conduit surrounding the central conduit and defining an annular passageway for carrying the exhausted driving fluid, mechanical means surrounding said flexible hose and coupling the lower end of the outer conduit to the vibrating head so that said annular passageway communicates with the exhaust port of the vibrating head, said mechanical means including means which affords a high impedance to transmission of vibratory energy from the vibrating head to the outer conduit, and means supporting the central conduit on the outer conduit.

2. Apparatus of claim 1 wherein the central conduit includes an enlarged portion having an upstream opening and a downstream opening, and wherein the filtering means comprises a first perforated pipe coupled to the upstream opening for discharging driving fluid into said enlarged portion and filtering out any large particles, a second perforated pipe coupled to the downstream opening and a screen disposed around said second perforated pipe, so that the driving fluid flowing into the second perforated pipe from the enlarged portion is filtered for fine particles by the screen before journeying on to the vibrating head.

3. Apparatus of claim 1 wherein the means Supporting the central conduit on the outer conduit comprises a perforated pipe intermediate in diameter between the outer conduit and the flexible hose, said perforated pipe being connected at its upper end to the central conduit, extending coaxially with the flexible hose and the outer conduit for a distance, and connected at its lower end to the outer conduit.

4. Apparatus of claim 1 wherein said mechanical means includes a hollow cylindrical member having a rounded collar portion protruding from its exterior surface, means coupling one end of the cylindrical member to the outer conduit, a gasket of flexible material surrounding said rounded collar portion, a hollow cylindrical assembly surrounding said gasket and separated thereby from the cylindrical member, the cylindrical assembly being tightened onto the gasket, and means coupling the cylindrical assembly to the Vibrating head.

5. Apparatus of claim 4 wherein two additional collars are disposed on the cylindrical member respectively above and below the rounded collar portion, said collars being spaced a short distance from the cylindrical assembly for limiting any movement thereof relative to the cylindrical member.

References Cited by the Examiner UNITED STATES PATENTS 2,340,959 2/44 Harth 166-177 2,670,801 3/54 Sherborne 166177 2,743,090 4/56 Malan 166177 2,816,612 12/57 Hutchison et al. 166177 2,918,126 12/59 Bodine 166-177 2,918,127 12/59 Bodine 166-43 3,016,093 1/62 Bodine 16643 3,045,749 7/62 Brandon 16642.1

CHARLES E. OCONNELL, Primary Examiner. 

1. IN APPARATUS FOR PRODUCING MECHANICAL VIBRATIONS INCLUDING A FLUID DRIVEN VIBRATING HEAD HAVING INTAKE AND EXHAUST PORTS FOR THE DRIVING FLUID, THE IMPROVEMENT WHICH COMPRISES AN ELONGATED HANGER ASSEMBLY FOR SUSPENDING AN OPERATING SAID VIBRATING HEAD WITHIN THE CONFINES OF A WELL BORE AT LOCATIONS ABOVE THE BOTTOM OF THE WELL, SAID HANGER ASSEMBLY COMPRISING A CENTRAL CONDUIT FOR CARRYING THE SUPPLIED DRIVING FLUID, MEANS DISPOSED INSIDE THE CENTRAL CONDUIT FOR FILTERING THE DRIVING FLUID BEFORE IT REACHES THE VIBRATING HEAD, A HOSE OF FLEXIBLE MATERIAL COUPLING THE LOWER END OF THE CENTRAL CONDUIT TO THE INTAKE PORT OF THE VIBRATING HEAD, AM OUTER CONDUIT SURROUNDING THE CENTRAL CONDUIT AND DEFINING AN ANNULAR PASSAGEWAY FOR CARRYING THE EXHAUSTED DRIVING FLUID, MECHANICAL MEANS SURROUNDING SAID FLEXIBLE HOSE AND COUPLING THE LOWER END OF THE OUTER CONDUIT TO THE VIBRATING HEAD SO THAT SAID ANNULAR PASSAGEWAY COMMUNICATES WITH THE EXHAUST PORT OF THE VIBRATING HEAD, SAID MECHANICAL MEANS INCLUDING MEANS WHICH AFFORDS A HIGH IMPEDANCE TO TRANSMISSION OF VIBRATORY ENERGY FROM THE VIBRATING HEAD TO THE OUTER CONDUIT, AND MEANS SUPPORTING THE CENTRAL CONDUIT ON THE OUTER CONDUIT. 